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Why did the speed of this plane drop so much?
(Disclaimer: I know nothing about aviation. It is not even a hobby to me. I'm sorry if this question sounds obvious or silly to experts.)
I was casually checking the arrival time of a flight on FightAware when I came across this strange speed profile, apparently for a routine flight between Korea and Japan:

(Reference: https://ja.flightaware.com/live/flight/AAR152/history/20171009/0035Z/RKSI/RJSS)
Indeed, it seems that the speed of the plane went slowly down, in a controlled way, and reached 380 km/h for about 5 minutes. Then it went up again, much faster, and came back to its normal value. The event had no influence on altitude.
As I said, I am no aviation expert, but... 380 km/h at 10,000 m seems SO SLOW to me! The speed was more than divided by 2 and actually came close to the speed of a train. To my knowledge, I’ve never been on a flight that slowed down so much in mid-air (and it would freak me out).
I then checked many other speed profiles to see if it was a common pattern, but I couldn’t find anything close to this. How could one explain such a steep decrease in speed? Is it a common occurrence or a rare safety issue? What usually causes this kind of event?

My guess would be for traffic separation at the destination airport. That seems a rather significant drop in ground speed, though, so I'd guess that there were also some errors in Flight Aware's data gathering and/or reporting. They're not perfect.

The perfectly straight lines would also suggest poor data acquisition during this stage. Suggesting that the drop is just two poor data points where the ground speed was being misreported. During the climb there is a similar but less obvious jump aswell to the same speed.

I think you've spotted the opposite effect of what @FreeMan posted. This is a possible duplicate: https://aviation.stackexchange.com/questions/16610/why-did-the-flightaware-groundspeed-readout-suddenly-spike-for-this-flight/16611#16611

Errors in Flightaware. You are basically looking at an unofficial source for historical air traffic data

Funny, @Jamiec, that's the same Q&A I linked to... :)

When you're in an airplane, how do you know how fast it's going? How would you even know it slowed down?

@Harper that’s another question, one that has probably been asked already, look for how is airspeed measured.

@Notts90 I was referring to the OP's context where s/he is sitting in a coach seat 30 rows back.

@Harper not sure what that has to do with the question...the speed data is from flighaware not seat 30. At no point did they say they were on the flight (that I can see). If you mean the bit about it feeling the aircraft slow/accelerate in general anyone with a functioning inner ear can feel acceleration, especially significant changes. Also some aircraft, mostly long haul, have screens that give you real time speed, altitude and outside air temp.

@Harper You can absolutely have a basic sense of speed as a passenger in a commercial flight. There are reference points (geographical features, clouds, lights, etc.), there is motor noise, there are screens giving you various informations, etc. There is no way a sudden speed drop from 1000 km/h to 380 km/h would go unnoticed by anyone.

If this data were legit it could be throttle down for some kind of noise control zone, but the loss of airspeed does seem too extreme for that.

@Harper You'd certainly know if your plane sped up or slowed down that much, that quickly. As in any other vehicle, you feel pushed into your seat when a plane accelerates hard and pulling forward against your seatbelt when it brakes hard.

At that point, altitude shows about 11 km, or FL330. Up there, 380 km/h, or 205 knots true corresponds to something like 124 knots indicated, well below clean stall speed.
This is ground speed though, so with very strong head-wind it could be possible. But the only sufficiently strong wind is the Jet stream and flying eastward they would have it in their backs.
Also for westbound flight, the dispatcher would have to make rather big mistake to send them across the jet stream—they do take forecast winds aloft into account when preparing the flight plan.
Data error is the only plausible explanation here.

You are right that this seems odd. An A320 would not be able to sustain flight at such a low speed at that altitude. Your reference data is erroneous. Don't trust everything you see on the internet.

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How do commercial pilots keep situational awareness of their current call sign?
Air transport pilots operate flights with a variety of flight numbers, often with multiple flights in the same day. This means, as a result, the callsign that they are using changes as well. Also, according to this answer, sometimes the callsign is completely different from the flight number.
Given that, how do pilots maintain keep track of what callsign that they are listening for at a given point in time? Are there conventions for posting the callsign somewhere in the cockpit?

From listening to LiveATC, sometimes you'll hear pilots mess up their callsign, sometimes even saying the wrong callsign (saying their other aircraft callsign for instance) and then correcting themselves. Usually pilots write it down somewhere from what I've seen, and usually only have to remember a few digits/numbers or your company ("Speedbird", etc) for your ears to perk up, then you can listen while reviewing your notated callsign.

@snakedoc quite often I hear them say the callsign of their previous flight

In cases where the flight number differs from the callsign, would the pilots even have much reason to care what the flight number is (or at least to care enough to maintain continued awareness of it)? That's for ground personnel and cabin crew.

Some modern airliners have a place where the flight number can be displayed on the cockpit displays. This information can be entered off the dispatch paperwork when setting up the flight plan, and is displayed throughout the flight for easy reference.
For example, you can make out "DLH463" on the screen at the bottom right of this Lufthansa A380 cockpit photo, corresponding to Lufthansa flight 463.
The Boeing 787 has a similar feature:

The two outboard displays are a fixed format that provides primary
  flight display information combined with an “auxiliary” display that
  consolidates frequently referenced information for the crew, such as
  flight number, each pilot’s microphone-selected radio and its
  frequency, and transponder code.

You can see this on this 787 cockpit photo at the top of the leftmost monitor: "FLT -> BAW787"
(Photos not embedded due to licensing restrictions.)

Besides crew reference, the callsign is downlinked in Mode S transponder data, so all airliners have some place to enter the callsign.

Changing call signs (or tail numbers) is fairly common from even early training. Its something that many pilots are accustomed to even before they get to the big operations.
As a student pilot its quite possible your flight school will have a few airframes usually of a given make. You may not always fly the same airframe and will get accustomed to rotating tail numbers. I did all my training in one of 3 Piper Warriors all outfitted the same.
From there many who plan to go to the airlines get their commercial ticket and instruct first to build their hours. While students will only fly a given type of airframe instructors may fly all the various makes the flight school owns. The last instructor I was flying with in any given day usually flys one of two Archers, An Arrow, one of 3 172's and a 150 all with different tail numbers.
Some pros may go on to fly 135 charts if they are lucky. Often times smaller chart outfits will have a variety of small aircraft that are constantly flying short hops and rotating crews allowing plenty of practice at hopping call signs/tail numbers
Once at the ATP level you already have a lot of hours flying a variety of planes, often all in one day.
Many smaller aircraft have a placard with the tail number affixed to the panel somewhere (like in this citation cockpit).

(source)

If the flight number written somewhere in the docs an airline pilot has immediately to hand?

@DJClayworth I think it does appear on the dispatch info delivered either on paper or via table these days.

@DJClayworth I don't know about now, but in the 1990s at the rwo 747 carriers I flew for, the flight number was at the top of the paper flight plans we used at the time. Each crew member had a copy. The pilots typically kept theirs on a clipboard close at hand. The flight engineers usually kept them laying on their desk.

There's a space below the compass. It seems to be reserved for a Post-it note :)

@Harper the space bellow the compass is for the compass correction card

I might be particularly dense but I'm having a hard time finding the answer to the question here. Is the implication that pilots are so used to frequently changing call signs that they quickly become good at remembering the call sign they are currently flying under, and don't need any method beyond their own mind to keep track?

@ToddWilcox more or less that is correct, and also that the mind suffices to the point where there is no hard and fast other method/rule/device that is standard across the board.

The 737 has it on the yoke where the right hand would rest. It doesn't affect any systems but you can turn the numbers to represent a 3 digit integer.

You can also see the callsign you entered when filling out the flightplan page in the fmc when pressing the "PROG" button on the fmc

This worked well back in the day, but it isn't terribly useful anymore, since airlines have gone to 4 digit flight numbers. It's now a plastic plug in the 737MAX, replaced by a 787-style display.

The first time I saw a post-it was in the cockpit of a Flying Tigers 747 in the early 80s, stuck next to the standby altimeter with the flight number on it (ie FT66 or similar).

I fly several different types of aircraft, in varied missions. So I can keep track of it, without making a radio fool of myself, I carry pink Post-its, and throw the callsign I am to use on my kneeboard or on the yoke.
Experience has taught me to avoid posting it on the panel, as the vertical position, plus sometimes high airflow can cause "callsign loss" which is on par with the embarrassment of "callsign error." Also, I used to use any color of Post-it, but experienced "callsign obscurity", and found that uniquely using a deep and bold pink reduced my radio stress.
As for others? I preach conversion, but there are few adopters and multitudes of critics. Look and see how many pilots carry a short stack of small pink Post-its on their kneeboard.

source: Stack Exchange

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Is there any certification for Aircraft Security that Software Engineers can accomplish?
I would like to ask you if there is any certification that Software Engineers can take for learning the fundamentals or more exeutive concerning the section of Air Safety and Security. I am talking about Safety protocols like DO-178C or DO-178B or any other.
*It doesn't really matter if it is going to be a US certification or a EU one.
Thank you in advance for your time.

You could start with RTCA DO-326A, Airworthiness Security Process Specification.  RTCA also has other documents focused on specific areas.

@Gerry what is the process? How can I read for this certification? How can I give the exams? Can you help me a little bit? Thank you.

There's no individual certifications. Any business or individual developing products for aircraft have to develop them in compliance with the airworthiness standards. The company's processes and procedures have to be compliant (SW development process must comply with DO-178C, etc.) and in the end they have to demonstrate to the FAA that their design is compliant to the rules. DO-325A defines a process for ensuring products meet the necessary level security. The best way to learn it is by doing it.  I knew nothing of the rules when I started working for an avionics company 24 years ago.

@Gerry could you please help for this? I don't know if this is for the topic of my question, but the reason I am asking all these is because I want to work for Avionics industry. I am good in C and Linux OS. I am trying these days to learn Ada and LynxOS for the aforementioned purpose. Could I ask you more things? If that is possible...

@Gerry could you write an answer instead of putting information in the comments?

@Gerry has indicated some of the specifications that apply to aviation software engineering, I think the OP is asking if there is something like the COMPTIA Network+ certification (which is applicable to computer networking) but would certify that the bearer of the certification has specific, test certified knowledge of those specifications and able to employ them in his/her software writing endeavours.

@Gerry is quite correct. There isn't an individual certification class you can take to become "certified" as a software engineer for aviation. You really have to learn by getting a job at a company that develops avionics software that already has a DO-178 compliant process in place. You'll soon find out that everyone's process is different.

You note DO-178C here, but the question seems to be about security.  DO-178C is about high-integrity software development (things like test coverage, requirement writing, safety analysis).  It is a big deal and applies to security but isn't strictly about security. DO-326 on the other hand, while not required for many applications, is one of the current standards directly addressing avionics security.

I am unaware of any individual certifications for engineers related to avionics - security or general SW development. Caveat: This is based on my experience. That's 24 years of civil avionics development which followed a USAF career in R&D, mostly space systems. I'm an aero engineer by schooling and my work is primarily defined as 'systems engineering' and management.
Fundamentally avionics development is no different than any other product development. We define and develop hardware and software to perform specific functions on aircraft. The skills are essentially the same as the auto industry and even some consumer products. For the software side, this means real-time embedded applications -- not PC, web, or client/server apps.
The biggest differences to other markets is the level of regulation and the life span of the products. Everything we build has to be certificated as part of an aircraft under a Type Certificate (TC) or Supplemental Type Certificate (STC) or as an 'appliance' under a Technical Standard Order (TSO). And even then the TSO'd product installation has to then be certificated under the aircraft's TC or STC. Because of the regulations, change is expensive so the products tend to have a very long life span. There are updates along the way, but you very seldom see wholesale product redesigns until the product is almost unsupportable or there are changes in the regulations.
Certification is about demonstrating that the product complies with the rules. In the US, that's Title 14 Code of Federal Regulations. That means focusing the entire business to meet the rules. That includes internal development processes and procedures and a quality program that's compliant.
Industry standards such as SAE, RTCA, (and EUROCAE in Europe) are the basis for most of these internal procedures. RTCA DO-178C doesn't tell you how to write code. It sets a standard for a SW development process that will produce the necessary artifacts for certification and theoretically result in SW that meets the necessary level of safety and design integrity. The company has an internally defined software development process that is compliant with DO-178.
As for security, RTCA DO-326A, Airworthiness Security Process Specification provides guidance. It doesn't tell you how to build a secure system. It defines a process that will allow you to identify the security risks and ensure that you address the risks.
So what's the best way to learn the avionics business? Seek employment with an avionics company. Avionics is a niche business. There's no big educational pipeline to feed the industry. If you have the fundamental engineering skills and a willingness to learn, you can get a job in avionics. That was the basic criteria I applied when I was a hiring manager at my last employer.
As to the basic skills; For a SW engineer I would look for SW design and coding experience. Real-time embedded experience is a definite plus but not a deal breaker depending on the specific job. Most companies I'm familiar with use ADA, C, C++, etc. Getting familiar with the industry standards helps (and shows initiative) but it won't make you an expert.

@selectstriker2  You are correct, and the text is corrected.

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How does the mounting surface flatness affect radio altimeter reading?
It is recommended that the antennas be installed on flat surfaces. For some UAVs, the bottom of the fuselage is very narrow and sharply curved away from the antennas. How does it affect the measurement error?

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How fast can pushback tugs actually go? (maximum possible speed)
For school, I'm doing a project where we choose a topic about anything, ask questions, and learn about it. I chose my topic as fuel efficiency of airplanes, and one of the things I want to research as part of that topic is fuel efficiency of planes on the ground and see if we can cut down fuel burn at airports. While I was exploring that sub-topic, I thought about tugs and if they are capable of going faster than 30 kts. If they are, we can use them more than just for pushback and potentially cut down on aircraft fuel use.

Are you thinking about towing aircraft on take off roll?

No. I was mainly thinking that a tug could tow aircraft to the main taxiway and then aircraft could go on their own power the rest of the way. Even though it might not be such a huge reduction, at least it's something- a lot of times aircraft are held up even before the taxiway before the runway.

You might want to take a look at electric wheel taxi systems too then, since that seems relevant to your project and avoids some of the operational problems of using tugs.

Thanks. I'll check it out.

This AC covers a lot of the regulations around towing aircraft and according to the regulations

Towing Speed. Towing speed should not exceed that of walking team
  members. Towing speed should not exceed the safe operating speed for
  the conditions or the published speeds established by the TLTV
  operators published procedures.

In other words you can do either as fast as your operator says you can or as fast as the tug manufacturer says you "safely" can. The AC goes on to discuss a lot of other things but also mentions this tug in their section on tow-bar-less tugs. According to their website:

Unique hydrostatic drive for moving aircraft on the ground at up to 32
  km/h [~20 MPH] – without compromising safety

This is about the same speed that Terry discusses is the maximum taxi speed in this answer so you don't really gain any speed. Depending on the aircraft and airport in question you don't want to cut down taxi time to much as that may be an important time during which the engines come up to temp.


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How long are the nacelle strakes on a GE-90?
For my school project, I'm doing something where I create a nacelle strake on a model plane and I want to make it to scale. Could you please let me know the dimensions of a nacelle strake? I would greatly appreciate it!!

You can measure this on photos.

Find a nice side view that shows the nacelle strake.
Measure the engine diameter on the photo.
Find the engine diameter in the engine specifications.
Calculate the ratio between the two. This gives you a scale factor of the photo.
Measure the strake, multiply by the scale factor to give the size of the strake on the real engine.
Divide by the scale factor of your model to get the size of the strake on your model.

I use a spreadsheet so I can do step 2-6 once. I then create a formula that converts a dimension I measured on the photo to the one I need on the model. Makes it easy to do lots of measurements on a photo.
I usually import the photo into an application that uses SI measurement units (Adobe Illustrator), but you can measure in pixels too (which allows you to use cheap image tools).

While complex, this sounds like a better option than "go to your nearest airport, wander out to the apron with a tape measure and a ladder". ;)

This is not an actual response but hints meant to help. Steps suggested by Hobbes are usually how it's done, but I'll dig in more in details.
About finding a photo, it's quite hard because the strake is on the inboard side. Most if not all photos are highly distorded due to perspective and you can't take the shot far enough from the opposite side as the fuselage kicks in. Most photos doesn't display the entirety of the engine, or are not large enough to make precise computation (such as those photos taken below and from the side of the aircraft on final, you can clearly see the strake and the entirety of the engine). By experience, I recommand flickr for such photos. You can get high resolution from authors (usually, a mail explaining your goals will do, but you may wait a week or much more before getting the photos for obvious reasons)
Alternative 1
High detailed 3-views from the manufacturer (including the company who designed the strakes). Best views are vector drawings (DXF), but it's not usually free and if you don't have an account to pay online (just like me) that's a no-go. But if you can, don't forget the strake is tilted, the measures  you get from the top view are not the actual size, the strake is slightly larger. Get the angle from the front view and do the appropriate computations. It's worth to note that, any drawing is the numerical hand made or formula-generated copy of the real thing, and there will always be some errors.
In the same principle, you may directly contact someone among the finest views drawers out there. One that come to mind is Jennings Heilig. I know he made drawings explaining the differences between the 777 engines (as related in this DAC post - I don't have J.R. Heilig contact) Those views builders uses the Alternative 3 below.
Alternative 2
Some Aviation SE members do build scale models, but due to the mass variety of questions about aviation, they may not spot this one or they have other things to do right now. The point is, scale model builders usually have detailed drawing of the model, and perhaps even the dimensions of most components of the aircraft. The Boeing 777 has several types of engines and some scale model documents explain the differences. Why not ask on a scale model forum like finescale or DAC ? By narrowing the potential readers to the ones highly caring about scalings and proportions, you may have the answer faster.
Because scale models are commercial products, you can't undisclose drawing informations contained in the build manual. But you can ask for precise information privately.
Alternative 3 is a mix of all those, extremely time consuming, where you're doing the thing yourself (DIY) and cross check everything. Actually, I started this as I'm 3D modelling the 777 right now, but I'm not yet carring about the strakes. The Boeing Airplane Characteristics for Airport Planning is a PDF document. Unfortunately, not only the most detailed views is for the 777-200F, but the strakes are missing from the top views (only there for the front view). And here you have a perfect example of drawing error : Distance from nose tip and engine cowling tip is 84ft 6in for the Boeing 777-300ER in the document. But that's wrong, the Boeing 777-300ER have longer engines (GE90-115B), the distance is for one of the -300 model (not ER) with shorter engine nacelles (I don't know for sure PW, GE or RR). The point is not to blame Boeing, but to explain why you should be very carefull not 100% thrusting a drawing even if it comes directly from the manufacturer. Small errors like that usually happen.
It's worth to note that you should select the appropriate engine from the start. The strakes are probably different for each type of nacelle.

Boeing 777-200(ER) and 777-300 have 3 types : GE90-9*, PW and RR
Boeing 777-200(LR), 777-200F and 777-300ER have one type : GE90-11*
Boeing 777-8X/9X have one type (not in service yet)

Find the photos with the target engine. You can use several websites like this one to identify which engine is installed on which airframe.
Now, you have the drawings, layer them with appropriate photos taken from far away (those from below and the side). Note that the 777 engines nacelles are nor perfectly circular, and doesn't look like truncated ellipses from the side, but slightly distored. You should take account of the fact that the 13ft diameter is not the diameter of the nacelle, but the distance between the highest point and the lowest, which are a few feet apart in a vertical projection. The nacelle width from a top view is slightly narrower (but most drawing views from top blindly assume 13ft is the max width of the nacelle). It's pure try and narrow error margins.
Use aswell rivets and seams lines from detailed photos to pinpoint the most precise location of the strake.
Further more, the engines are tilted, both in the horizontal plan, and the frontal plan. When measuring the strake (SI units in appropriate tool or pixels in a drawing tool), you should either un-tilt the engine, or do the appropriate computations. What I'll would do is get the most precise projections in the views, draw the strake 3D, and measure the distance between points... but I'm nowhere to get there yet I don't have the time to in the next weeks.

Boeing DXF Drawings are here
Boeing Airplane Characteristics for Airport Planning are here

And just a personal opinion : Unless you're doing some sort of airfoil specific experiment/demonstration with an 1:5 or larger scaled model replica, most people won't care about on-scale or not the moment proportions are kept realistic. Keep in mind the size of your model and the materials you'll use to make the replica : are your materials thin and easy to precisely cut enough to respect proportions, while being strong enough to not fall apart upon handling..??


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Should you blow through the final approach course if the ATC forgot about you?
So you were being vectored for the final approach course (ILS/RNAV/whatever) and the controller forgot about you for some reason (busy). Assume you called them and they were not replying. Also assume you were not yet cleared for the approach but they told you to assume the x approach. Would you blow through the final approach course and wait for them, even though you might conflict with traffic, or turn inbound even though you had not been cleared and potentially take a beating later?

Yes, blow right through it.  You should never deviate from a clearance to "take a beating" later simply because you think you know better than the controller.  If the controller is busy it is for a reason, and it is very possible they are extending you on purpose for spacing.  You could very well conflict with traffic even more by taking your own turn.  It is far better to let them fix the overshoot they caused than to battle the FAA over a flight violation.
If you genuinely think the controller may have forgotten about you, you should continue to attempt contact, while pressing IDENT with each transmission.  If it is so busy that you can't get a word in edgewise, press IDENT anyway.  I have done this and received an immediate turn without even having to transmit on the radio.  It is designed to get their attention, just don't overuse it.
The only exceptions where you should deviate from an assigned vector are if you are lost comm or have an emergency.  In either case make sure you are squawking appropriately.
I would consider a vector towards terrain a pending emergency if not turned within some appropriate period of time.  When I was instructing in the Navy, during simulator rides I would force a missed approach at McChord AFB, give a climb to 5000' and a left turn towards Mt Rainier.  I would then fail the crew's radios.  It was always a good lesson in terrain awareness, especially for young aviators from flat states.

Thanks.  It was a technique I was taught early on in case you need to get their attention and it always seemed like a good idea to me.  And a good way to acknowledge ATC when you can hear them, but not transmit.  Actually, I think military radios have a selectable function where IDENT engages any time the mic is keyed.  Good idea for a single pilot lost comm scenario to avoid having to take hands off the controls.

Excellent scenario - lost comm when vectored into terrain! What outcome would you expect? Join approach before Mt Rainier, I guess?

Would simply reaching a border of a zone with a minimal vectoring altitude lower than your current altitude constitute an emergency?

@Vladimir f- Good question.  Short answer is yes, I would consider being below MVA in IMC to be an emergency.  The degree of my response would depend on the circumstances though.  For example, let's say I was at my home field and had excellent situational awareness on the area, and a very good moving map dispaly.  If I knew I was just inside a sector with a ridge of mountains, and I am in an out of the clouds so that I can also visually confirm that I am following a river parallel to a ridgeline 5 miles to the side I would be more patient with ATC, and debrief them on their error after I land.

However, if I am at an unfamiliar airfield with lower awareness due to steam gauges I wouldn't be passive at all.

@Cpt Reynolds- I seem to recall mainly doing it off the missed approach to the south heading runway, the expectation being that they would get an initial vector, followed soon by clearance direct home base NAS Whidbey.  I think the students would have had a better chance of catching the blow-through of final if they were on base leg.  The mountain is far enough away that I doubt many would drive right into it during an approach.

It's an oddball situation because normally once you are put on a heading that will intercept final, the approach clearance is included with the heading instruction ("XXX, turn right heading YYY, cleared for the approach").
But lets say the controller actually just gave you a heading to final and nothing else, and you never heard from them again.  The question becomes, is this a valid comm failure or not.
If it's a real comm failure, and you continue through the final approach course and just continue off to who knows where, what is the controller to do for separation of traffic?  You are now like a horse that escaped the barn, and the controller now has no idea of where you are going next.
Assuming all efforts to raise ATC fail, you go to the basic IFR comm failure procedure and proceed logically based on the comm failure protocol; clearance, expected clearance, and all that.  In this case it's pretty clear to expect the approach you are being vectored to.
So if it was me, I would be frantically trying to make contact but once I was convinced I had a real comm failure I'd select 7600 and just fly the approach.
Once ATC sees the 7600 selection, that's what the controller will expect me to do and will be able to adjust traffic flow to suit.  That last thing to do in a comm failure situation in a terminal area is to head off in unexpected directions.

You make some good points, and I agree that if you have a strong suspicion of a comm failure is it best to recognize it and take action early, before getting too far across the inbound course and making things more difficult.  However, I would caution about being to hasty if you know the controller is busy...

Agreed.  The scenario given is really not very realistic I think.  It's unlikely a controller is going to turn you to intercept the LOC without an approach clearance at the turn and if he does he's really screwed up.  A more likely scenario is a vector for spacing, like on a downwind leg of an arrival, where the controller is distracted and you think it's time to be turned in and no instruction comes. Well in that case you stay on your heading unless staying on the heading is getting you in danger somehow, while you work out whether you have a comm failure or the controller is just busy.

authors: Vladimir F Героям слава


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When will the Canadian ADS-B satellite system be implemented?
It is interesting that ADS-B is not mandated in Canada as of yet. If you fly in the US you quickly realize the benefits. Now as I understand it Nav Canada is the largest shareholder in Iridum but ADS-B in the SDA (Southern Domestic Airspace) is still far off.
Some people may hate the idea of a mandate but I fly in the south and it is crucial to be able to see other traffic. XM is great for WX but expensive. I am curious as to why Nav-can is not hot on the ADS-B trail other than the politics of mandated dollars for Mode-S transponders.
Does anyone know the timing for implementation of the ADS-B satellite system for Canada?

What is the SDA?

This Advisory Circular, although from 2011, is still current and indicates that there will no Transport Canada ADSB mandate (being regulatory, it's not up to Nav Canada).  It appears the policy is to foster voluntary adoption of ADSB over time, and Nav Canada will create an environment where aircraft operators will get operational benefits by adopting it.
So the commercial world will likely switch over fairly quickly, while GA operators and private owners will do it gradually as the costs of the systems come down, and anyone who doesn't want to doesn't have to, and can continue using Mode C. I imagine that later on, when the system is mature, say in 5+ years from now, and GA ADSB systems are dirt cheap, TC/Nav Can will likely decide it's time to phase out surveillance radar completely, and then it'll be mandated for anyone that wants to operate in transponder airspace.

Roughly 90% of Canadians live within 100 miles of the US border, which is trivially crossed in a plane, so it's likely the Canadian fleet will see similar adoption to the US fleet: 100% for turbine and urban piston operators by 2020, with rural pistons slowly following. Canada doesn't really need a mandate of its own until they want to phase radar out entirely.

Yes I understand that . ADSB has interestingly been available in the far north in canada for a long time. ( as I read it maybe even long before other areas adopted it ).I find I lose the u.s adsb benefit 30-40 miles north of the Great Lakes. it is  helpful but not cheap so I understand the mandating issue.

While it's technically true that TC may no mandate ADS-B, that circular does say, "It is acknowledged that ADS-B technology will supplement the current ground-based radar surveillance system and may eventually replace it to some extent, however, the intent of not mandating the ADS-B system is to allow owners and operators to volunteer their participation in a surveillance system where NAV CANADA will offer ADS-B and to benefit from its advantages." Realistically though, the "benefit" that operators will be see is the ability to enter certain airspace or perhaps be limited in their operations.

Just to clarify something to start, NAV CANADA is not a majority shareholder in Iridium Communications Inc., but rather Aireon LLC (the provider of space-based ADS-B service). The Aireon payload is a "hosted" on each of Iridium's NEXT satellites.
NAV CANADA has completed its Aeronautical Study for a Canadian ADS-B Out Performance Requirements Mandate and the Aeronautical Study Plan Summary is available publicly. The current plan includes the first two phases of the mandate:

Phase 1: Class A airspace (which includes 18,000ft ASL to FL600 in the Sourthern Control Area, FL230 to FL600 in the Northern Control Area, and FL270 to FL600 in the Arctic control area)
Phase 2: Class B airspace (All low level controlled airspace above 12,500ft ASL or from the minimum enroute altitude, whichever is higher, to below 18,000ft ASL plus some terminal control areas or control zones)

While not quoted in the study summary, Phase 1 is proposed for implementation January 1, 2021 and Phase 2 on January 1, 2022. Beyond Phase 2, no sooner than January 1, 2023, Class C, D and E airspace as required and following additional stakeholder consultations.
To you comment about "seeing" other traffic, the current infrastructure is not set up to re-transmit traffic information for ADS-B "In" equipped aircraft. Based on the Technical Specification, Aireon only detects up the "Out" transmission from 1090 MHz Mode S transponders but is unable to detect 978 MHz UAT transponders.
So all that to say, unless you're flying above 12,500ft ASL, the ADS-B Mandate will not be affecting you for at least a few years and you will not be seeing ADS-B data coming from the Aireon constellation, only the ADS-B broadcasts from other aircraft directly in the vicinity. There is no ground infrastructure in Canada which broadcasts TIS-B or FIS-B data so you will not see aircraft equipped with Mode C only.


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WW2 Bombers continuing on one of 2 or 4 engines, how would that work?
I think I recall stories of damaged bombers making it home with only one of the original 2 or 4 engines functioning. But I visualize the plane being severely unbalanced if a single engine was propelling the plane and then simply going in circles or, worse, a tight spin.
My only guess as to how such a handicapped plane would be able to successfully fly is that the unbalance was somehow compensated for using the rudder and/or other control devices. But even then, it must have been pretty dicey and the plane might have trouble keeping up air speed sufficient to stay aloft.
Of course, perhaps my recollection is wrong and only a plane with a single non-functional engine out of 4 could actually fly successfully and if a two-engine plane lost one engine, then the plane would not be functional.
I wonder if modern two-engine jets somehow can fly on one engine and I vaguely recall such cases.

The number of engines is mostly necessitated by the runway length, not airspeed.

Two engine planes are generally designed to fly on one engine. It has (almost?) always been the case. It takes a lot more power to take-off than maintain flying. So while planes may not be able to take off with half the number of engines running they can easily keep on flying.

Not relevant to the question as written but possible of interest - modern twin engine passenger aircraft are required to be capable of both takeoff and long distance flight on a single engine. https://en.wikipedia.org/wiki/ETOPS. Part of this is being cautious on payload - if loaded up like WWII bombers were they would not be able to do this.

"No matter what they do to her, the Gooney Bird still flies/One crippled ship was fitted out with one wing half the size/She hunched her shoulders, then took off -- I know this makes you laugh/One wing askew and yet she flew: the DC Two-and-a-Half! "

Twin engine airplanes being able to fly on a single engine is normally a design certification requirement. In the case of twin-engine airliners, they must not only be able to fly on just one engine (sometimes for 5+ hours at a time,) but also continue a takeoff and climb out on a single engine if an engine fails during takeoff after reaching the V1 speed. While a given person is unlikely to experience a jet engine failure, in the context of the entire aviation industry, they happen many times per year and are generally more-or-less non-events.

The typical case is that twin-engine airplanes can absolutely fly with one engine shut down.  This being possible means that the extra engine provides redundancy; if such an airplane couldn't fly in that condition, the second engine would double the chance of a flight-ending engine failure occurring.
In order to keep the airplane controllable when one engine is at full power and the other is shut down, designers take steps like keeping the engines fairly close to the fuselage so that the "leverage" -- the moment arm -- of the asymmetric thrust is reduced.  They also ensure that the tail surface and rudder -- which provides the force to counteract the yawing moment caused by the unbalanced forces -- is large enough to do so under any expected conditions.
From a pilot's perspective, the greater the airspeed, the more control authority the rudder provides, so in an engine-out case, you want to keep the airspeed high enough that your rudder input can balance out the asymmetric thrust.  It's also possible to add a little bank toward the operating engine, which also helps to balance things so the airplane flies straight ahead rather than turning continuously toward the failed engine.
For a 4-engine aircraft that's lost 3 engines, the additional concern is a lack of power to keep the airplane aloft.  Depending on the weight of the aircraft, a single engine might keep the airplane in level flight without losing airspeed, but more probably some amount of descent would be required to avoid losing speed (and, eventually, once the speed decayed enough, losing control as well).  How far you can get would depend on all sorts of factors, such as how heavy you were to start with, how much altitude you have to work with, if the winds are pushing you along, how much other damage is adding drag to the aircraft, and so on.  Maybe the B-17 can't get all the way back to England with 3 of 4 engines shot out, but if they can get to France, or to the English Channel, the odds of avoiding capture after bailing out get better.
If you had a light enough 747 or A380, you might maintain level flight with one engine, but at most weights you'd probably be trading altitude for airspeed.  With two of four engines operating, you could hold level flight at some significantly higher weight, though probably well below max takeoff weight.  Any 4-engine aircraft should be able to fly fine on 3 engines, since otherwise you'd be at the point where any (single) engine failure on takeoff is unsurvivable, and that's not an acceptable scenario.
Altitude is also a factor; losing an engine up high near the service ceiling may mean a "drift down" to an altitude at which max continuous power on the remaining engine(s) will hold level flight + maintain airspeed.  If that altitude is above the terrain, then all is good; if it isn't then the crew will need to use the time & distance available while drifting down to head toward lower terrain, or (worst case) toward wherever they prefer for the forced landing to take place.
The max load you can carry might have to be reduced so that you aren't too heavy to keep flying with one engine out; pilots regularly practice (in the simulator) what happens if an engine fails right at takeoff, just after the point you can no longer stop the aircraft on the runway.  If you (and the aircraft) can fly out of that scenario, all other cases are less demanding.  How much weight you can have at takeoff, based on engine-out climb performance (and other criteria) is something that gets computed based on the particular conditions of "this" flight.
Left to its own -- i.e. if the pilot didn't make any control inputs to counter the asymmetric thrust, then the aircraft would continuously turn into the failed engine, and things wouldn't end well.  But, part of the training required to be able to fly a multi-engine aircraft is learning how to do so even with an engine failure.  That's been the case basically since aircraft with more than one engine started flying, and certainly continues today with 2- and 4-engine airliners.

Your point about building a plane that required two engines doubling the chance of a catastrophic failure (especially when you are being shot at while on bombing missions) is a very good one. What a heck of a job being part of a WW2  bomber crew must have been. The upside was sleeping in a bed or at least a bunk each night, but that was assuming you made it back. The planes were not too comfortable either. But I guess it was pretty exciting.

At least with a bomber it’s easy to get rid of the payload to reduce weight ;)

Sometimes WWII four-engine bombers could maintain altitude on two engines, if they had burned off a lot of fuel and dropped their bombs. It was easier if the live engines were not on the same side. I doubt any could on one engine, but you got more choice about where you came down.

...and only turn in the direction of the functional engine. BTW one of the most strange (imho) airplanes ever built is Rutan's Boomerang which, according to wikipedia, "[...] was intended to be a multi-engine aircraft that in the event of failure of a single engine would not become dangerously difficult to control due to asymmetric thrust."

@releseabe While they get to rest at "home", the bomber crew had 3 times higher chance of dying compared to the rest of the military. It was brutal. The mortality rate of the 8th air force (US bomber command) was around 7% compared to around 3% for Marines, 2% for Army and less than 1% for the Navy. Part of the reason was the strategic use of the planes themselves (rather than the bombs) as bait to reduce the number of enemy planes in preparation for D-Day.

@slebetman: wow. and i know the planes were cold and generally uncomfortable. but i believe i read that being an airman, especially a fighter pilot, was considered very prestigious. But a fighter pilot, what a scary job: Roald Dahl describes being very inexperienced and finding out he would get virtually no training. He survived by the skin of his teeth.

@releseabe I don't think bomber crews were directly told this but the strategy was to use the bombers to lure enemy fighters and for the fighter escorts to then hunt down and kill those fighters. This was to reduce airborne threats during the invasion later. They've never done it again after WW2 because it was too costly. 7% is almost one in every ten men lost. If we include those captured by the enemy it's easily one in every ten men not coming back.

Yes, you can fly an airplane home on one engine on a twin very easily. Multi engine pilots are trained to do that in an emergency situation.
The difficulties in operating such an airplane on only one engine is you have very limited climb performance and airspeed control.  An engine failure causes a loss of at least 50% of total thrust available to you and 80% of your climb and maneuvering performance.  It may also be the case that a multi engine airplane cannot maintain altitude or climb at all on a single engine, even when flown at the best rate of climb speed for single engine operations, Vyse.  In certain cases of an engine failure during cruise at higher altitudes, the airplane cannot maintain cruise altitude and is forced to drift down to at or below the airplane’s single engine service ceiling.  If your flight plan was predicated upon twin engine operations to clear mountains or other terrain taller than your single engine service ceiling, An engine failure could be very hazardous as you cannot maintain an altitude high enough to clear terrain.  In wartime, this could be hazardous if you are trying to clear airspace defended by anti-aircraft guns and an engine failure causes you to drift down within range of them.
The Tony Scott film Top Gun features an inaccuracy in the climatic dogfight sequence near the end.  There is a scene where enemy MiGs jump Iceman’s six and score hits on his F-14 with cannon fire. Iceman’s RIO inform him that they were hit in the right engine to which Iceman responds by shutting down the affected engine and remains in the fight.  In reality, his F-14 has now lost at least 50% of its total available thrust and at least 80% of its climb and maneuvering performance.  In the real world, the only choice Ice would have is to bug out of the fight and see if he could nurse his damaged Tomcat back to the ship - if, that is, the MiGs will let him leave without jumping his six again and blowing him out of the sky.
The other hazard in the event of an engine control is airspeed.  Operations at lower airspeeds are demanding and can be very hazardous if you cannot or do not have proper control over your airspeed in these situations.  There is a speed in multi engine aircraft known as Vmca at which the tailfin and rudder can no longer maintain directional control if an engine is inoperative.  Flight at speeds below that with the good engine at maximum power will result in loss of control.  If the airspeed is properly maintained at or above Vmca, the pilot can still maintain directional control using the rudder, if they maintain a slight bank angle of not more than 5° away from the good engine.  It is also worth noting that flight at or close to Vmca only offers directional control.  It is NOT a safe maneuvering speed for the aircraft and accidents have occurred when pilots have attempted to aggressively maneuver an airplane around Vmca.
Takeoffs are also a very risky time for an engine failure at low air speed As an airplane is operating at full power/thrust while trying to gain airspeed.  Loss of engine power in a twin can cause loss of control easily during the takeoff roll and once airborne if the pilot does not react quickly and correctly the counter the situation.  The typical procedure in twins is to use a takeoff decision speed, V1, which is the maximum speed at which the pilot may abort the takeoff roll and stop the airplane with runway remaining using braking alone.  It is also the minimum speed, at which should an engine suddenly become inoperative, a pilot may continue the takeoff on only one engine and achieve the takeoff safety speed, V2, at least 35 ft above the departure end of the runway.  It is worth noting as well that the decision speed V1 is well above Vmca/Vmcg, thus assuring directional control in the event of an engine failure. Pilots train for an emergency procedure involving an engine loss right at V1.  This is known as a V1 cut.  In jets the resulting thrust asymmetry is not as severe as it is with propeller, driven aircraft and much easier to manage given the performance guarantees inherent to the design of transport category airplanes.

Four-engine transports flying "The Hump" in WW2 could not maintain enough altitude if they lost just one engine. Same for the two-engine transports, but they were more reliable since they had fewer engines that could fail.

I flew the P-3 Orion for the US Navy which is a 4-engine turbo prop.  On almost every training flight I ever flew on we would practice flying, landing, and stopping with two engines simulated to be shutdown (both on the same side).  This was accomplished by setting a known power setting that simulated having the propellers feathered (no thrust, and minimal drag).
It was not easy.  Maintaining sufficient air speed was critical, because as others have said here controllability is critical with all the thrust coming from one side of the plane, and it is very easy to get in a position that you can't recover from.  It took a ton of rudder input, and even with rudder trim, it was tiring.
In the real world, the worst thing that I ever had to deal with was a 3-engine landing, and it was one of the inboard engines, so almost not noticeable.  Even with perfect conditions, a 2-engines out (on the same wing) landing would have elevated my heart rate a bit.

Possibly also relevant, I understand Orion's routinely patrolled on three engines to maximize endurance? Relevant to the part of OPs question about flying on three of four engine being exceptional/dangerous rather than something of a default for the P-3, despite being low over ocean.

Yeah, I misread the question.  3 of 4 not a big deal and we did routinely shutdown one, and there was a procedure to shutdown two of them (not on the same side) to save fuel when down low.  Flight school was the mighty King Air, and we practiced single engine landings in that as well.  Also not a huge deal.  It flew fine on one.

Did you guys always shut down an inboard for that, or was it a matter of rotating the engine among all 4 to keep service life about even?

There are generators on 2,3, & 4.  The engine driven compressors that provide environmental support (cabin heating and cooling) and pressurization are located on 2 & 3.  So #1 is the choice to loiter.  The vertical stab and rudder on a P-3 is huge so this was not a big deal.

Here's part of the training manual for a (4 engine) C54 Skymaster, a WWII transport plane: Part 2

If you think you may ever find yourself with only one engine left, study the sections of this book on ditchings and emergency landings carefully. The proper procedure in this case is to start looking for a clearing.

There is also advice on flying with 2 engines:

With two engines out in a lightly loaded aircraft, it is possible to maintain altitude.

And with 3 engines:

Use roughly 10% less air speed [...] Always turn away from a dead engine if practical [...]Trim for unequal power by relieving the rudder pressure with the rudder trim tab.

I immediately though of the Skymaster because that did happen to my ancestor. They came into Midway with just enough altitude for the wheels to clear the runway.

Good stuff - the tech orders were a lot more plain-spoken back then! Welcome to Av.SE!

I wonder just how functional a 4-engine plane with just one engine is. Is the advice because the plane is not really flyable or is it actually  able to fly, but the assumption is perhaps that whatever happened to 3 of the engines might well happen to the final engine and that would be it.

A 4-engine plane is flyable on a single engine, just as it is with no engines (depending on how the flight surfaces are moved).  The issue is that on one engine it will not be able to maintain level flight.  The single engine will extend the range it can travel over gliding, but it is certainly going to be in a descent.  This is why the training manual referenced above says to start looking for a clearing.  Kind of like Ron White said..."One engine has got enough power to get you to the scene of the crash, which is good...because that is where you are headed".


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How does an airline decide on an engine?
How does an airline, when buying aircrafts, decide on which engine to use? In many cases, although there are several options to choose from, the engines do not differ much in their operating parameters.
As an example I would take the Boeing 757-200. This aircraft was able to be equipped with Rolls-Royce RB211 and Pratt&Whitney PW2000. Both engines have very similiar performance ratings and also do not differ much in their physical parameters (e.g. diameter, weight).
From this perspective, it seems to me, that engine decisions are mostly driven by business consideration (e.g. sales discounts, maintenance contracts...)?

I guess, as many equipment, maintenance expertise with the manufacturers products and financial/commercial agreement are important

I think you are answering your own question. It all boils down to money. Every factor of the aircraft buying process will be driven by money. They are, after all, a business. Some decision driving factors may include:

The acquisition cost.
The operating cost.
Fuel efficiency. Fuel costs the airline money
The reliability. Down time for the aircraft loses the airline money.
The liability. Is it going to breakdown midflight and cause death and lawsuits?
Manufacturer support. Will they get help if problems arise?
Is their an adequate supply chain of parts?
Airline’s specific history with that engine.
Does the airline already have mechanics certified and experienced for that engine?
Do they already have parts and spares of that engine?
It is easier to maintain only one type/model of engine across their fleet than several.
Tax incentives.
National loyalty for some airlines.
Brand loyalty for other airlines.
Kickbacks
TBO. Maintenance costs money.
Core resale value.
Possible advertisement opportunity.
Contractual agreements.
Politics (both internal and external)
Etc.


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How do I pick the right ATC channel to listen to my flight?
I'm trying to listen to my flight's ATC communications (flying United out of SFO). What is the difference between ramp, ground, and departure channels? Ground and departure have multiple frequencies, so I'm wondering which ones I should listen to for my flight?

What are you using to monitor the channels with?  Some stuff may be digitally transmitted, so you might not even hear it.  If you don't know your flights call sign, you may not pick on stuff intended for your plane. Some stuff may have shortened frequencies, such as the use of ".9" vs "121.9", so you could miss those too.

In order after you're seated, I would choose (assuming you can find and listen to them):

Company ops/ramp (possibly specific to your airport sector ie. where
you are on ground)
SMC (may have another name), but 'Surface movement
control' which allocates pushback instructions, and taxiway
allocations to your departure runway
Tower to hear runway approval/cleared for takeoff, and SID if allocated
Departures after takeoff to confirm your routing in the terminal area
En-route control - occasional messages as you follow your flight plan
Arrivals at the other end to receive STARs or vectoring instructions
Tower for clearance to land
SMC for taxiway guidance
Airline Ops for instructions towards gate, connecting gate info (crew and pax). Airline Ops may also receive engineering follow ups required after arriving at gate.

There's a lot of channel changing to do all this!


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Why does transonic drag happen?
I have heard of transonic speed and it is between supersonic and not supersonic. What is it and why does it happen to aircraft and how does it produce a lot of drag. How do you prevent it from happening?

Airflow around aircraft and especially over wing is not uniform. The lowest transsonic speed is when the airflow at some point of aircraft (usually over wing) goes supersonic. Depending on aircraft, this happens around M0.8. When the airflow around entire aircraft is supersonic the transsonic region ends.
The excessive drag is due to the shockwave(s) that forms in the airflow at the location where airflow has accelerated to speed of sound. As airflow ahead of it hits the shockwave the energy of flow dissipates and there is sudden drop in air pressure across the shockwave. As there is less pressure behind the shockwave than there is in front of it additional drag is induced in the process. This called wave drag.
This effect can be counteracted by designing an airfoil that forms the shockwave initially as close as trailing edge as possible and then the entire airfoil goes supersonic as quickly as possible as speed increases. See https://en.wikipedia.org/wiki/Supercritical_airfoil
The formation of shockwave is the reason why supersonic aircraft has pointed noses as air is not pushed ahead of an aircraft. The pointed nose creates an oblique shockwave that has creates less drag along the aircraft flight path.
Pointed cones can also be seen in engine intakes of supersonic aircraft (see SR-71 and Mig-21). The additional oblique shockwave formed by the cone ahead of the engine is used to slow air entering the engine to subsonic speeds. The cone is moved back and forth as mach number changes to keep the shockwave away from the actual engine. Concorde used adjustable ramps within engine intake for same effect.

thanks :) really helpful!

That was a helpful answer, but how exactly is this drag force transmitted onto the surface of the wing? To me, this point does not seem as intuitive as for example "form drag", where the force is clearly transmitted onto the surface due to surface friction. Can wave drag exist with zero viscosity effects?

@AdityaSharma It cannot. Wave drag is induced by miniscule imperfections on the wing surface. Layer of air next to the wing that becomes stagnate does not propagate pressure wave upstream as the stream has reached supersonic speed - thus again stopping abruptly next layer as it hits stagnate air. So it is eventually the wing surface that stops ever increasing amount of air, causing the drag. The drag can be so substantial that it was called “sound barrier” as engines of the time could not overcome it.

@busdriver Makes sense, thank you!

As I understand it, total pressure (i.e. static + dynamic in incompressible region) decreases across a shock. Wave drag is due to the difference in total pressure across a shock (larger upstream than down stream).
On the other hand, static pressure increases across a shock wave causing an adverse pressure gradient downstream leading to flow separation and a further increase in drag.

Welcome to aviation.se. Do you have any sources or references?


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What happens if a plane breaks down away from a maintenance facility?
I am curious about what happens when a large plane, such as a commercial passenger jet, has an equipment problem at an airport where the company does not have a maintenance facility.
For instance, do airlines have mechanics at every airport that they serve? And do those airports have a supply of spare parts?
Even if those answers are no, I imagine it's easy enough for an airline to fly in parts and staff. What happens if the repair requires some large piece of equipment to complete?

Related: What is this orange container labeled “Flight kit wheel”? Sometimes it's good to travel with spare parts :-)

One month ago, an Airbus A380 flying from Paris to Los Angeles landed at Goose Bay, Newfoundland, after one of the turbojets disintegrated in flight. The airliner can't be repaired at Goose Bay, and the management of Air France and the FAA are still discussing what to do and how...

And in February, Swissair had to fly in an engine, crew, and tent to fix a Boeing 777 http://avherald.com/h?article=4a453674&opt=0

There are a lot of possibilities to handle a broken down aircraft, depending on the location and the extent of the damage.
First, to answer the question about mechanics: airlines do not keep mechanics at every airport they fly to. If the airport is a destination of a flight, it is chosen such that it is equipped to service the type of aircraft that will fly there. Repairs are done locally at the airport: after all, a Boeing 757 from Airline X is just like another Boeing 757 from Airline Y, from a maintenance point of view.
Now that may not be true if the airline is flying to a remote location or a not-so-developed country. IIRC an answer from a retired 747 captain on this site states that the flight engineer is also a qualified mechanic and they carry tools in the cargo hold to deal with simple repairs. I am not sure if this practice is still in use today.
If the repair cannot be completed at the airport, it is usually a result a diversion, an emergency landing, or unusual damage. There are two options: either repair the aircraft on site back to service status, or patch it up temporarily so it can fly to a location where better maintenance is carried out.
The airline can use whatever means to transport the necessary equipment there. However a grounded aircraft is an asset not making profit, and the quickest way to shuttle equipment is by flying. The airline may fly engineers and tools from the main hub using its own planes, or it may charter a cargo flight.
If the damage is really serious, the aircraft manufacturer has an emergency response team that go anywhere in the world to fix an aircraft. The team is on-call 24/7. Members of the team are very experienced mechanics who worked at the assembly line, and they can repair almost any damage.

Also interesting reading about the logistics of remote maintenance: http://www.popularmechanics.com/flight/airlines/a25590/changing-worlds-largest-engine/

I’ve done it both in the military and the civilian world. At major airlines, it’s pretty rare that you’ll fly into a place without mechanics. That said, there are odd circumstances as pointed out in other answers. In those cases, we do our best to coordinate with the pilots to get a very good idea of what the problem is.
Usually Maintenance Operations Center techs will try to find a local mechanic or even someone from another airline to get it going. Generally speaking, if the problem was that simple, the pilots probably didn’t need to divert anyway. Other airlines don’t mind helping with parts, but manning is another story. There are labor contract issues, payroll problems, etc... It gets complicated quickly. That’s usually when they call The Mothership and decide to bring a few mechanics in to fix it.
From there, we brainstorm most likely scenarios and also the most outlandish. We try to bring everything including the kitchen sink. From experience, no matter how easy you thought it was on the phone, and no matter what you bring, there is a guaranteed monkey wrench lurking in the midst. After all, if this was just any ordinary problem, the plane would have been off the ground already.
We usually dispatch to the plane by other commercial flights, or we drive to the location ourselves. Most guys prefer to drive because we’re usually on overtime for the majority of the trip... Might as well drive 8 hours on OT too...
Once we arrive, the mess we’re in quickly becomes apparent. We usually hem and haw in gaped astonishment at what went wrong. Then we realize that nothing we are looking at is what we were told over the phone. Then we call The Mothership and explain that we need some outlandish piece of equipment. It then becomes MOC job to get us that equipment somehow or some way. Still on OT, we make our way back to the hotel and wait for the call that our stuff is on the way.
I have changed engines with skyscraper cranes, performed wire splaces with two terminals, a bolt, a nut, and a piece of tape, and made adjustments to “non-adjustable” equipment to get a plane off the ground and into a better location. Sometimes you have to be creative but judicious in the repair process.
Usually, after days of lack of sleep and suffering from overexposure to cold, heat and/or other intolerable elements, we get the airplane up and go home. After our arrival, we fill out our travel paperwork, are summarily haggled to death by bean counters who have no idea what we have  just done, and find that the 47 hours of OT we were billing the company for gets knocked down to about 12 hours plus a few denied receipts. In the end, you break even, go home, lie to the wife why there is a $2000 charge for “The Dollhouse” on the credit card and go to bed. Later that evening, you’re called to go on another trip and the cycle continues.

If anyone puts sitting in the hotel and unnecessarily long journeys down as OT I think they should expect it to be declined  unless of course you’re genuinely doing actual work in the hotel/car. As much as we’d like it, no one is going to pay that rate for sitting around! Also don’t forget to ask the bartender to put your tab on the bill as a food order

Nice work and family ethic! (BTW, both the bean counters and wife understand the extra OT and nature of the dollhouse)

It depends on the extent of the problem, the availability of mechanical personel and of course on the local availability of spares. About flying in parts and staff, it may not be easy at all, depending on the location of the airport and the distance from the manufacturer and /or airline location:
as a typical example, several years ago an Alitalia 747 had a substantial engine problem which caused the pilots to land in Canberra, Australia, instead of Melbourne. Having found and ascertained the extent of the problem, Alitalia decided to adopt the quickest and relatively less expensive option: a new engine was secured to the wing of an other 747, which was flown empty from Rome (Italy) to Canberra. Here the defective engine was taken off the grounded craft and the new one was installed. The total repairing time was about 4 days, which meant that the grounded 747's downtime was comparatively very little and the financial loss to the company was the minimum possible.

Do you know if the 747 from Rome ferried an extra (5th) engine, as in this story? http://www.dailymail.co.uk/news/article-3392372/The-plane-nervous-flyers-Massive-Qantas-jumbo-jet-flies-Sydney-South-Africa-FIVE-engines-attached-wings-airline-deploys-rarely-used-transportation-method.html

I was flying a night hop out of NAS Cecil Field near Jacksonville, Florida. At that time it was home to the Sidewinders of VA-86. I was headed south and Tampa was on my right wing when the hydraulic warning came on. I was in an A7-E which had 3 hydraulic systems. If you lost one the aircraft still flew fine, but emergency procedures dictated the pilot land as soon as possible. I declared an emergency and checked to see if I could get fuel and a start at MacDill AFB. I landed there, and the squadron detached a maintenance crew to the airport to fix the hydraulic system. It took a few days to repair and was flown back after that.
What I found most interesting about the emergency is that, after getting back to the squadron, the Maintenance Officer told me he would have brought the aircraft home on 2 systems. At the same time he told me that a pilot would never be faulted for following emergency procedures.

One thing to be considered is the company's willingness to fix the broken airplane due to cost considerations.
In the late 80s or early 90s a certain asian carrier had a ground strike on one of its outboard engines (747) in Manila. This engine was not usable and instead of ferrying an engine in (this airline had 747 freighters and was based in Asia) they elected to ferry the airplane out. A three engine ferry on a 747 is not really that bad especially as it was only a few hours back to base but some airlines only allowed crews who have trained specifically for 3-engine ferries to perform the flight. Some airlines even go to the extent of paying Boeing crews to ferry these aircraft. Well to cut a long story short they went off the runway during the take-off run and the poor plane got stuck in the mud. This airline had been going thru a bad patch with a widebody crash almost every other year.
Another scenario is a certain airline from a middle east country which has been under a trade embargo for a long time.... oh all right Iran Air. Anyway this airline would 'never' ground the aircraft off base. I'd bet that even if the engine fell off they would rather bring the aircraft home rather than pay for off-base engineering which is 'very' expensive. If you work on an airport which handles this airline you will notice that they usually have their own ground engineers. This is because a contracted engineer may be bound to report an unsafe aircraft to the authorities.
Back to parts.. a lot of airlines maintain reciprocal agreements with other airlines. Eg Lufthansa and Singapore (as an example) would probably work out a deal where if SQ needed a tyre in Frankfurt, LH would loan one to them and vice versa in Singapore. On return the tyre would be accompanied by documentation stating how many landings the tyre had done and LH would bill SQ accordingly. You would be surprised that even sworn enemies will help each other as you never know when you'll need help! Only exception is if their own stock is low then they may not be able to release because they need to be prepared in case their own plane breaks.
Aircraft which do a lot of ad-hoc flying will carry a flight kit and engineer on board. Stuff like filters, tyres, oils and other things which usually cause problems on that type are usually carried. These thing will usually get you home even if it doesn't cure the problem. Eg a component like a pump may be faulty and the aircraft MEL (minimum eqpt list) may state that pump must be removed. Well you probably wont have the pump in the spares kit but you may have a blanking plate and seals so if you remove the pump and blank off the drive hole then you'd be good to go, back to base at least!
Finally a lot depends on the culture the airline comes from and the attitude towards regulations. A pilot from one country would never fly a plane his colleague from another would cheerfully take to the skies. We all bitch and moan about the regulations but at the end of the day I'd rather be late than dead.


text:
How does the B-2 Spirit fly without a rudder?
On the B-2 Spirit bomber there are no rudders on the back of the aircraft, how does it fly without entering a flat spin or losing control, because when other aircraft like commercial liners lose their rudders it usually ends in a crash?

Birds have no rudders, and fly quite well...

If you must have an image in your post, please attribute it. In this case, the B-2 is one of the best-known modern airframe designs so it's debatable whether you really need a photo at all.

It uses a fly-by-wire system to actively maintain stability, and uses split ailerons at the wing tips for differential drag for yaw control.


text:
What causes the nose landing gear knocking noise on a Boeing 777 while taxiing?
The NLG knocking noise heard on taxi-in to stand, what could cause this knocking noise?


text:
Why are airline seat belts lap-only?
On the flight that I was on today, one of the passengers near me asked this question. Why don’t airplanes use lap- and shoulder belts like cars do?

Closely related, maybe a dupe?

@Pondlife Yes, this is a duplicate. I did not see that question in my search. Thank you.


text:
Why does ADS-B broadcast velocity?
I just read on opensky-network (scroll down to the section "facts") that ADS-B transmits roughly as many velocity as position messages.
Since the velocity of an aircraft can be computed from two successive position  broadcasts, why is the velocity transmitted directly?

The "position" and "velocity" include more than what the title would suggest.
Airborne position gives you:

Latitude/longitude
Altitude

Airborne velocity gives you:

Horizontal ground speed vector
Vertical rate
Air speed (when ground speed not available, can be true or indicated)
Heading (when ground speed is not available)

Together these two message types give you all the basic information you need about an aircraft's location and velocity. You are correct that given two lat/lon/altitude points, you can calculate the average horizontal speed, heading, and vertical rate. Keep in mind that ADS-B is already using the Compact Position Reporting format which calculates position with either two sequential messages or a reference position.
In addition to the additional computation cost, the measurement accuracy also needs to be considered. ADS-B broadcasts a "Navigation Integrity Category" or NIC, which expresses the accuracy of the GPS position. In terminal airspace, ADS-B is required to have about +/-300 feet in positional accuracy. While this is sufficient for giving general position and providing separation, it would create a lot of error in computing velocity. In reality the positions are fairly consistent but data errors still happen.

The reasons why successive position estimates are NOT utilized on GPS receivers for determining velocity vectors include: 1,) position updates are 1Hz and have substantial individual position errors, 2.)velocity estimates utilizing Doppler with 4 or more SA and the local clock, is continuous, and with an extremely low computational cost, 3.) ALL modern aviation GPS units have internal velocity estimates which are intrinsically MUCH more accurate than simple positional estimates.

Why is airspeed only transmitted if ground speed is not available?

GPS receivers can get very accurate velocity vector information.  It is part of the receiver architecture, and does not require a separate processing of prior positions.
So the velocity information is "free" and actually is much more accurate than the position information.
From a global architecture standpoint, it is far preferable to provide the velocity vector than it is to defer the calculation to a ground station, and because of the accuracy, it is desirable to use the velocity vector from the receiver rather than to rely of historical points to calculate that velcity vector value.
Those are factors in the architecture of ADS-B and the data fields.
Addendum #1:  The OP asks, "Since the velocity of an aircraft can be computed from two successive position broadcasts, why is the velocity transmitted directly?"  There are two parts of the answer. The first is that the velocity information is available from the GPS receiver and is magnitudes more accurate than the position estimation, and happens at a much higher rate than the position estimations needed for a velocity estimation. The OP surmises that successive position estimates can be used for a velocity estimation, but a velocity estimate determined that way will have substantial error, and latency.  The second is that the standard says that velocity information will be transmitted.  Of course it was designed that way because the continuous, low latency and high accuracy velocity information was available from the GPS (utilizing the Doppler of each SA L1 carrier against the local clock or other method).

I was not aware of the fact that using a GNSS yielded an accurate velocity vector. This explains a lot, thanks. I will read more about the receiver architecture.

Within the industry, this is well known, but for a variety of reasons, not well written about in the open literature. The single channel receiver on the Garmin 90, a couple of decade old aviation single channel GPS unit, was accurate to nearly millimeter velocity determinations even when SA was turned on. In the mid-1990's I was developing GMTI algorithms. To test accuracy we would push a car on a flat country road, and test our radar algorithms. We verified the speeds, which were well under 1km/hr using GPS velocity estimations.

While almost all the designs are proprietary, a common method employs Doppler off SA, using the pseudo range rate equations. The velocity information from the 1Hz position updates is very noisy and not very accurate. The Doppler can be calculated with the local clock, and is a couple of magnitudes more accurate.  Only older very cheap handheld GPS use successive positions for velocity, and for decades marine and aviation units have used Doppler or similar methods for very accurate velocity estimations. The $9 GPS chips I get use a TDCP methods.  ref: http://www.insidegnss.com/node/4433

If you have someone trying to tell you that GPS utilize successive position estimates for velocity vectors, I suggest that you consider other sources of expertise, as this has not been the engineering practice for decades, and those sources are not providing information representative of the current practice in the art.

Thank you for your insights. It raises another question: what is the application for such precise velocity measurements? But this is out of the scope of this question, and probably even of aviation.SE. An idea where I can ask about this?

@Gab, it is a big deal in quite a few sectors of position, navigation and time (PNT). For example, if you are navigating a rocket, and controlling the trajectory, the rapid velocity estimate updates are far more useful than the rather spaced out (1Hz) position estimates. That means one can effectively manipulate the control surfaces on the rocket with tighter tracking control. It is less of a big deal when there is a hiker in the woods, and spurious position or velocity estimates can be tolerated.

It sounds logical to have the velocity (speed) data in the ADS-B messages rather than computing it.
One of the reasons is the computational cost on the receiver side. In order to calculate the speed of a broadcaster from position data, the receiver must first translate(convert) the difference of consecutive positions into a distance unit (meters?). Then it must divide that value to the time-difference between two messages. It's totally unnecessary if the broadcaster is not a concern at all. However, if the speed is high enough, you'd have to mark it as a potential threat (for collision).
Now, suppose that you're receiving signals from 1000 broadcasters simultaneously, you'd have to 1000 computations simultaneously and continuously. This is a problem of scales.
On the broadcaster side, speed is a readily available value, and it takes little effort to broadcast it.

Why would a GPS receiver system "translate" position information to velocity information when the User Range Rate Error of US GPS is <0.006m/sec over any 3 second interval, with 95% probability? Simple knowledge of GPS receiver attributes and the ADS-B application of GPS data makes the "translate/convert" mentioned superflous! In reality it does not happen that way.  Stated differently, show me an ADS-B and GPS pair which do it the way described.

@mongo maybe my answer is misunderstood. I emphasized the same as you said. Doing the mentioned calculation off-board (on another aircraft) is a waste of resources.

A fine point is that there is no need to do a calculation locally, the data is already there in the GPS receiver, using the Doppler shift of each satellite off the local clock, and it is far more accurate than utilizing successive range estimates.

Sure, the question is essentially asking about calculating the speed of one aircraft A on another aircraft B using position of aircraft A only. I assumed that self speed is already known by aircraft A, in the last paragraph this can be seen. I didn't want to go into details of GPS and other systems. I think the question would be sufficiently answered by the architectural considerations.

And why would this be difficult for the receiver to do, exactly? 1000 simple calculations per second is nothing. Do 1000 simple calculations per nanosecond, and you have a small problem.

@user253751, Of course a computer can do the calculations, but transfering the velocity function responsibility of the broadcaster side to the edge causes a non-optimal architecture. It will certainly require some RAM and more computational power and will cost more to develop, and to build, and to qualify/certify.


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if your Seneca weight is 4000 pounds , and you have 800m visibility, would you take off?
An examiner asked me if your Seneca weight is 4000 pounds , and you have 800m visibility, would you take off ?
I said by law the visibility is ok but still I would not because if we get an engine failure, We can't maintain VMC or altitude  , but he wants me to explain more and better !??

Do not you think some runway is also required?

If you're asking "is it safe and legal to take off in a Seneca at 4000lbs and with 800m visibility?" then please let us know which year/model of Seneca, which country or regulations, how long the runway is, and any other information you think would help with the decision. Those details would help to get a more precise answer.

He probably would like to have a two-parts answer: first part demostrating you know regulations and aircraft performance, second part that you have commons sense. Being legally able to do something doesn`t necessarily mean it is smart to. I can (usually) legally go flying my glider when there is a paragliding competition near the field, still I never do.

What he wants to know most likely is do you have accelerate-stop and accelerate-go distances computed for that airport and ambient atmospheric conditions at that takeoff weight. Do you also have adequate runway available for that as well as a climb rate adequate for obstacle clearance in the event of a critical engine failure after Vr?  And if that’s the case, do you have a plan in place for that emergency situation?  Multi engine flying is a lot about anticipation for these kinds of contingencies.  Having a plan for takeoff and departure and anticipating engine failure on takeoff is all part of safely flying light and medium twins.  If you can’t do that, you’re in dangerous waters and the examiner wants you to think about that.
I don’t have a Seneca AFM available to me, but you should probably go back and review your takeoff and climb performance data for OEI as well as information related to your airport and departure procedures.  This should give you a much better answer to this question.
From a legal perspective, it also all depends upon under what flight regulations the flight is being conducted under.  With approx 1/2 sm visibility and flying a two engined aircraft, the departure would be illegal when conducted under Part 121, 125, 129, and 135 commercial operations, but is legal under a Part 91 flight operations.  Make sure that is included in your decision as well.
Finally, just because you CAN do something does not necessarily mean you SHOULD do something.  These conditions are pretty tight and you are painting yourself into a really uncomfortable corner with little margin for error should anything go wrong.  Are you really that competent to operate a twin, including handling an engine failure, with such low weather minimums or in complete zero-zero conditions?  Are you willing to bet your life on that knowing that once you’re airborne in that environment and on course, there’s no turning back?  Can you maintain the correct airspeed, altitude, heading, and climb rate which the AFM lists all while juggling an engine failure or some other emergency while in IMC?  Are you sure these conditions don’t exceed your personal minimums given your experience with multi-engine flying and, in particular, operation of a Piper Seneca?  If the answer is no, then you should not fly under these conditions.


text:
Why is it the ATC recording of Ethiopian Airlines Flight 302 is not yet available online?
I understand sites like liveatc.net constantly stream the conversation between the ATC and pilots. Why is it that there's no such recording for Ethiopian Airlines Flight 302 yet?

There are privacy laws in other countries that prohibit recording third party conversations. LiveATC is not available in every country for that reason.

For audio to be available requires two things. First, an actual recording has to exist, from ATC, CVR and/or public recordings. That may not be available in every part of the world. Second, whatever authorities are in charge have to release the recordings. That involves law, politics, and all sorts of other 'messy' stuff.  I don't know about this specific flight, but you certainly can't assume that flight audio is available in all cases.

If the recording has not surfaced "yet", it likely won't. LiveATC recordings are hosted by volunteers and are not "official." The "official" tapes rarely are ever heard by the public.


text:
Why are these flights not using a more direct route?
Why are the three flights (see image below) not using either Nepali or Bangladeshi airspace?  The five "freedoms of the air" should have allowed them to follow a more straighter path, instead of burning so much fuel, at altitudes of more than 30 thousand feet.

The "freedoms of the air" are conceptual framework rather than reflection of reality (fifth freedom flights, for example, are very often restricted), and even where a country grants air rights, they're still subject to national restrictions such as requirements to obtain overflight permits, pay navigation fees, use designated airways (sometimes more limited for foreign carriers) and avoid restricted airspace. Commercial aviation's desire to save fuel and time often must yield to political and logistical concerns.

Some countries have more strict rules regarding their airspaces - Nepal and Bangladesh are among them, requiring special permissions even to fly through it.
https://permit2fly.com/region/asia/nepal-overflight-permits.html
https://permit2fly.com/region/asia/bangladesh-overflight-permits.html
Though possible, it might not be worth the hassle and the costs - this small detour would only require very little fuel.
For Bangladesh this is even more strict, as there seems to be an active ADIZ:
https://en.wikipedia.org/wiki/Air_defense_identification_zone#Bangladesh


text:
What is the benefit of a large number of runways?
I noticed that Chicago Intl has 8 runways. What is the criteria for the number of runways? Many international airports still have one. I can understand the reason for two but what are the factors to create more? If one was to develop a new international airport today, what number of runways would they default to if there's such a default? What are the benefits?

More takeoffs and landings?

Amount of traffic. Busy eventually equals more runways.
Like your local interstate highways. Some places, 2 lanes. Some places, 8 lanes.
"International" doesn't mean much as far as amount of traffic. My local regional airport, PHF, is "international". It has a flight to Bermuda once a day. There are 2 runways, but one is rarely used.

In the U.S., and as noted in another answer, "international" in the name doesn't (shouldn't?) have anything to do with the size or the amount of traffic. Rather it is used to designate that the airport is an "Airport of Entry." In other words, there will be U.S. Customs and Border Protection there.
Insofar as the number of runways, I suggest that four is a good number to work with for a busy international airport: one for departures and one for arrivals for operations to and from the airport for 0° through 179° and another pair for 180° through 359° or whatever allocation makes sense.

As everyone else has mentioned, amount of traffic is paramount.  Airports commonly operate with several parallel runways active -- with departures and arrivals sometimes separated, but often interwoven.
In addition, the variability of winds can lead to a need for more runways.  At Ohare (Chicago's international airport), two of the runways are not parallel to the other six.  So in many regards, it really only has six runways that can operate simultaneously.
Atlanta has five runways -- all parallel.  Denver has six - four North/South, two East/West.

I will try answer point by point:
What is the criteria for the number of runways?

Amount of traffic is the criteria. The more traffic you have the more runway you need.

Many international airports still have one. I can understand the reason for two but what are the factors to create more?

They have more traffic than 2 can handle. BKK currently has 2 runways but master plan is for 4 runways to accommodate increasing amount of traffic.

If one was to develop a new international airport today, what number of runways would they default to if there's such a default? What are the benefits?

There is no default as it depends on amount of traffic. International Airport means it has custom and immigration. If the traffic is light one runway is suffice.
If you ask how to plan for a large airport I would suggest a plot of very large empty land for future expansion and good connection to cities you serve.


text:
Why can such a small difference in thrust make such a big difference in maximum speed?
I was recently comparing two aircraft, and, although I feel stupid asking this question, I wondered why one had a maximum speed of M2.2 compared to M0.94, when both have similar weight, both are supersonic capable and both have similar thrust.
Compare for example the Hawker Hunter F.6 which has:

Empty weight 6,406kg
Max speed M0.94 (>M1.0 In a dive)
Engine thrust 10,145lbf
Climbrate 17,200ft/min

And the Mirage F.1:

Empty weight 7,050kg
Max speed M2.2
Engine thrust 13,700lbf (WET)
Climbrate 16,400ft/min

As you can see, both have similar rates of climb, similar empty weights, and both are aerodynamically supersonic capable. Only major difference being the the F.1 has ~35% more thrust- yet, with this extra thrust and weight, it is able to go over twice as fast? How does this work?
As I write this the only thing I can think is that wave drag plays a part, and the afterburner is required to give it that extra boost to break through the transonic barrier?
If the above is the case, then does this mean that all aircraft that can supercruise require the use of afterburner to get there, but can then hold it in mil power? And, if so, could this mean theoretically you could use a rocket booster of some form to push the Hunter F.6 through the transonic region and hold a supersonic speed, or, is there a minimum thrust to weight ratio in mil power required to achieve supercruise, or do more special aerodynamics need to be involved to keep wave drag down to make it possible?

One possible mistake is in treating thrust as one single number.  It's not.  Max thrust varies a lot with altitude, temperature, and mach number.  What you are quoting is just one specific point (maybe takeoff?) If your engine is not specifically designed for supersonic flight, performance can drop a lot as you go up in speed.  I was not able to find any performance curves for engines in this specific planes (thus comment not answer), but I'm guessing that if you did, you might find a wide variation in performance vs mach number.

The aircraft were designed for different things. It's like asking why your road car with a 300HP V8 can't go 1-100MPH in under 2 seconds and brake at 5G+ while an F1 car with a 750HP V6 can.  Different specs. Different purpose. Different tools. Heck, if you pulled that V6 F1 engine and put it in your road car, you still wouldn't get that kind of performance. (It would be a whole lotta fun, though! :)

and both are aerodynamically supersonic capable

No, not really.

The blunt nose and rather thick wing with not all that much sweep of the Hawker Hunter are not suited for supersonic flight.

The engine inlets of the Hunter lack the (movable) shock cones like the Mirage, which are needed for flight at higher Mach numbers (either a movable shock cone or a variable inlet vane are needed above around M1.6), and the shape is generally not suited for supersonic flight. Supersonic inlet needs to create an orderly pattern of shock waves inside to maintain smooth air flow and the triangular shape does not look like it would do that.

Also the Hunter engine probably has lower exhaust velocity, which makes it more efficient, but limits the maximum power at which it can still produce thrust.

Ministry of Supply Memorandum 3420 shows in Fig. 9 the zero-lift drag of the Hunter up to Mach 1.2. While transsonic drag doubles for a good supersonic design, for the Hunter it increases by almost a factor of 5.


text:
How to calculate turbojet thrust at variable altitudes and mach numbers?
I am interested in developing a flight model in jbsim. jbsim requires a thrust table similar to as follows, with varying mach and altitude numbers (with thrust as a fraction of max):
     |  -10000       0   10000   20000   30000   40000   50000
-----+--------------------------------------------------------
0.0  |  1.2600  1.0000  0.7400  0.5340  0.3720  0.2410  0.1490
0.2  |  1.1710  0.9340  0.6970  0.5060  0.3550  0.2310  0.1430
0.4  |  1.1500  0.9210  0.6920  0.5060  0.3570  0.2330  0.1450
0.6  |  1.1810  0.9510  0.7210  0.5320  0.3780  0.2480  0.1540
0.8  |  1.2580  1.0200  0.7820  0.5820  0.4170  0.2750  0.1700
1.0  |  1.3690  1.1200  0.8710  0.6510  0.4750  0.3150  0.1950
1.2  |  1.4850  1.2300  0.9750  0.7440  0.5450  0.3640  0.2250
1.4  |  1.5941  1.3400  1.0860  0.8450  0.6280  0.4240  0.2630

Given that I know the thrust of an engine at sea level, in a standard atmosphere at 0 velocity, how would one calculate, or extrapolate the same data for something such as a J57-21?


text:
Are there any calculations involved for designing pulse jets?
Are there any requirements for calculations to determine things like exhaust length, combustion chamber size, etc? Also, does the end of the combustion chamber need to be a semi-sphere, or can it be flat?

Do you think it is remotely possible that the answer to the question is, "No, there are no calculations involved in designing pulse jets; they just guess at everything"?  Of course the answer is: "Yes, Aeronautical design is a math-intensive, rigorous subject"

Do you think it is possible to answer a question, no matter how dumb it may seem to you, politely? Or is this beyond your scope of ability?

Here you have something of interest: https://aardvark.co.nz/pjet/inside_pj.pdf

Thanks- I did find this calculator excel spreadsheet, which seems to answer my question. Now it's just finding the materials. :)

You can adjust the resonance frequency with the length of the jet using this formula. For the simplest pulse jets check out Colin Furze. This guy is not completely serious, but a genius nonetheless.

I'm reading that now- thanks :)

YES
There are calculations involved in the design of a pulse jet. (title question)
YES
There are requirements for calculations... (first body question)
NO
The end of the combustion chamber does not need to be a hemi-sphere. (second body question)

This may not actually be correct - chances are that if you had a fair sense of what a pulse jet should be, you could put together something via the "that looks about right" method which would sustain operation and produce thrust.  It wouldn't be ideal, but there's a fair chance it would work, or could be refined to by experiment without any calculation at all.  However, that is not the usual approach.  You can design airplanes by similar methods - they often fly, but you might not want to be on board when they do so.


text:
Why would a Blue Angels pilot leave their gear down?
In a recent Blue Angels airshow, one of the pilots had their landing gear down during the first 5 minutes of the show. What possible reasons would justify leaving the aircraft in this state?
No picture available.

Perhaps ironically because it makes a nice picture?

Trying to flow slow to give the amateur photogs a chance?